Hydroformemg process



United States Patent' HYDROFORMING PROCESS Charles N. Kimberlin, Jr.,and Elroy M. Gladrow, Baton Rouge, La., assignors to Esso Research andEngineering Company, a corporation of. Delaware Application March 4,1952, Serial No. 274,756

6 Claims. (Cl. 19650) This invention relates to the catalytic conversionof hydrocarbons and particularly to the hydroforming of hydrocarbonfractions boiling within the motor fuel range of low knock rating intohigh octane number fuels rich in aromatics by contacting these fractionswith metal oxide containing catalysts prepared in a certain way.

It is well known that petroleum naphthas can be subjected to reformingoperations to yield liquid products boiling within the gasoline rangeand possessing improved octane numbers. Reforming operations employingcatalysts, especially hydroforming and aromatizationprocesses are widelyused in the petroleum industry. By hydroforming is ordinarily meant aprocess wherein hydrocarbon fractions boiling within the motor fuel ornaphtha range are treated at elevated temperatures and pressures in thepresence of certain solid catalysts and hydrogen whereby the hydrocarbonfraction is increased in aromaticity with no net consumption ofhydrogen. The term aromatization when used broadly refers to conversionswhich increase the aromaticity ofthe hydrocarbon fractions treated. Asgenerally used in the petroleum industry, aromatization is a process inwhich hydrocarbon fractions are treated at elevated temperatures in thepresence of solid catalysts and in the presence or absence of hydrogen,usually at pressures lower than those employed in hydroforming, for thepurpose of increasing the aromaticity of the hydrocarbon fraction.

Catalytic reforming processes are usually carried out at temperatures ofabout 750-l150 F. in the pressure range of about to 3000 lbs. per squareinch and in the presence of such catalysts as molybdenum oxide, chromiumoxide, nickel oxide or sulfide or any of a number of oxides or suldes ofmetal of groups lV, V, VI, Vil and VIII of the periodic system. Thesecatalytic materials are usually dispersed or supported on a base orspacing agent. A commonly used spacing agent for this type of catalystis alumina either precipitated or of the gel type. Catalysts which givefavorable yields of aromatic gasoline components, particularly withcertain feeds and at relatively low pressures, have been prepared uponZinc aluminate spinel supports.

Hydroforming and aromatization are the most promising methods availablefor upgrading motor fuel or naphtha fractions because of the highyield-octane number relationships and because the products obtained tendto give less engine deposits than thermally reformed naphthas. in viewof the increasing demands for larger amounts of motor fuel of higheranti-knock characteristics, this field has been the subject forintensive investigation by many groups in an effort to find improvedcatalysts and techniques which will give larger yields and/or higheroctane number products.

lt is the object of this invention to provide the art with an improvedmethod for hydroforming motor fuel fractions.

It is also the object of this invention to provide the art with animproved vmethod for hydroforming motor "ice fuely fractions with highyield-octane number relationships.

It is a further object of this invention to provide the art' with amethod for hydroforming motor fuel fractions which permits highthroughputs of fresh feed and still yields high octane number products.

These and other objects will appear more clearly from the detailedspecification and claims which follow.

It has now been found that hydrocarbon fractions boiling within themotor fuel or naphtha range can be advantageously reformed orhydroformed by contacting the hydrocarbon vapors under reforming orhydroforming conditions with a hydroforming catalyst supported upon analumina or zinc aluminate spinel base, the pore size and pore sizedistribution of which is controlled and adjusted by dehydrating the samein the presence of an at most partiallyv water-miscible organic liquid.Normal butanol is preferred; however, isobutyl alcohol, secondary butylalcohol, isoamyl alcohol, secondary amyl alcohols, and the like ormixtures of these may also be useful. In the preferred embodiment analumina hydrosol is dispersed in the organic liquid, maintaineddispersedl therein until it has set to a hydrogel and is then dried incontact with the organic liquid to form dry, spherical, aluminaparticles that are characterized by possessing a low density and a highsurface area with a preponderance of large pores, i. e. larger than 50and preferably larger than Angstrom units in diameter. A group VI metaloxide, preferably molybdenum oxide is incorporated before or after thealumina gel is formed and dried. y

The catalyst base material or support is preferably alumina. The aluminamay be obtained from an alumina sol prepared by treatment of aluminummetal with a dilute acid such as 1% acetic acid solution in the presenceof mercury or a mercury compound or by hydrolysis under peptizingconditions of an aluminum alcoholate such as aluminum ethylate,propylate or preferably aluminum amylate in view of the ease of recoveryof amyl alcohol from the hydrolysis reaction mixture.

The alumina sol may be converted to the hydrogel and then dried incontact with the partially water-miscible organic liquids named above.It is preferred, however, to disperse sol droplets in the partiallywater-miscible organic liquid whereupon suicient water is removed toform spherical gel particles which, upon further drying in contact withthe organic liquid, are converted to the low density, high surface areacatalyst supports which are used in accordance with the presentinvention.

The catalytic metal oxides may be incorporated in a variety of ways. Forexample, the catalytic metal compound, for example ammonium molybdatecan be incorporated in the alumina hydrosol or it may be incorporated inthe set or dried alumina gel either by impregnation with a suitablesolution or by dry mixing molybdic acid or a heat decomposable compoundof molybdenum with the gel particles and heating to effect distributionof the molybdenum oxide upon the support.

Reference is made to the accompanying drawing illustrating adiagrammatic flow plan of a process for preparing microsphericalcatalysts that may be used in accordance wth the present invention.

Referring to the drawing, into mixing zone 10 are introduced alumina solby line 12 and dry normal butanol by line 1.4; the volume ratio ofbutanol to alumina sol is about 10 to l or more. ln mixing zone l@ theAlzOs sol is dispersed in the butanol in the form of small sphericaldroplets. The butanol extracts a part of the water from the sol dropletsthus causing the droplets to harden intosmall spheres of vhydrogel orsemi-dry gel. The suspension ofv gel spheres in butanol is transferredbyline 16 to distillationI tower 20 where the water is distilledoverhead in the form of the butanol-water azeotrope which passes throughline 22 and condenser 24 into water-butanol separator 26. The lowerlayer of Water containing a small amount of butanol is transferred fromseparator 26 by line 28 to distillation tower 30 where the butanol isdistilled overhead through line 32 and condenser 24 into separator 26.Water freed of butanol i's withdrawn from tower 30 by line 34. Tower 30may be heated by coil 36. The upper layer of butanol containing somewater is returned from settler 26 to tower 20 by line 40. The suspensionof dehydrated gel microspheres in dry butanol is withdrawn by line 42into settler 44 where it settles into an upper layer of clear, drybutanol and a lower layer of thickened slurry of gel microspheres inbutanol. A part of the clear butanol may be vaporized in heater 46 andreturned to tower 20 by line 50 in order to provide heat for tower 2G.The remainder of the clear butanol layer is returned to line 14 by line52. The thickened slurry of dehydrated gel microspheres is transferredfrom settler 44 through line 54 into uidized solids distillation zone 60which is heated by coil 62 and in which dried gel microspheres arefluidized by recirculated inert gas introduced into the bottom ofstripping zone 64. The butanol associated with the gel microspheres isvaporized in distillation zone 6i) and passes overhead with the uidizingand stripping gas by line 66 through condenser 68 into gas-liquidseparator 70 whence the gas is returned by blower 72 and line 74 intothe lower section of stripping zone 64. The separated butanol iswithdrawn from separator 70 and returned to line 14 by lines 76 and 52.The dried gel microspheres remaining in distillation zone 60 descendthrough stripper 64 where they are stripped of butanol by the ascendingstripping gas. The dry gel microspheres freed of butanol are removed byline 78.

The dried gel microspheres may be discharged from line 78 intoimpregnation vessel 80. Molybdic acid, preferably in dry powder form, isintroduced into vessel 80 y preferably 2 to 4 hours, in order to permitthe catalytic t.

metal oxide to become uniformly distributed over the support. Catalystdescending through standpipe S4 is picked up by a stream of air enteringtransfer line burner 36. Oil, gas, or similar fuel introduced by line 88is burned in transfer line burner 86 which discharges into the lowersection of impregnation vessel 80, thus providing heat and fluidizinggas to the contents of vessel 80. lt is important for best impregnationthat an excess of air be employed in transfer line burner 86 over theamount needed to burn the fuel, in order to provide an oxidizingatmosphere in vessel 80 and thus prevent the reduction of the molybdicacid to a lower state of oxidation. Other means of heating vessel may beemployed if desired. Finished catalyst is withdrawn from vessel 80 byline 90.

in place of the high temperature dry impregnation of the aluminamicrospheres, the latter may be impregnated by a wet technique with asolution of a molybdenum compound, if desired. For this purpose themicrospheres from line 78 may be treated with a solution of ammot niummolybdate containing the desired amount of molybdenum. The impregnatedcatalyst is then dried and, if desired, may be activated by hightemperature treatment, for example, at 1200 F. to 1300 F. for about 6hours. The finished catalyst may comprise from 5 to 20 wt. percent ofmolybdenum trioxide, preferably 8 to 15%. lf desired, variousstabilizers or promoters may be added such as the oxides of silicon,calcium, chromium, zirconium, titanium, zinc, or cobalt. Whenstabilizers or promoters are used, these may be added in amounts up toabout l0 wt. percent of the nished catalyst, but are usually added inamounts of less than about 6 wt. percent.

Catalysts prepared as described above are utilized in the hydroformingof motor fuel or naphtha fractions. The hydrocarbon feed stock may be astraight run or virgin naphtha, a cracked naphtha, a Fischer-Tropschnaphtha or the like. The feed stock is preheated alone, or in admixturewith recycle gas to reaction temperature or to the maximum temperaturepossible while avoiding thermal degradation of the feed stock.Ordinarily, preheating of the feed stock is carried out to temperaturesof about 800-l000 F., preferably about 950 F. The naphtha preheat shouldbe as high as possible while avoiding thermal degradation thereof as bylimiting the time of residence in the preheating coils as well as in thetransfer or feed inlet lines. The preheated feed stock may be suppliedto the reaction Zone in admixture with hydrogen-rich recycle gas or itmay be charged separately to the reaction zone. Contact of the reactantsand catalyst may be effected in a xed or a moving bed but is preferablyeffected in a dense uidized bed of finely divided catalyst particleswhich are continuously circulated from the reaction zone to aregeneration zone and back into the reaction zone. The recycle gas,which contains from about 50 to 70 volume percent hydrogen is preheatedto temperatures of about 1150 to 1200 F., preferably about 1185 F. Therecycle gas should be circulated through the reactor at a rate of fromabout 1000 to 8000 cu. ft. per bbl. of naphtha feed. The amount ofrecycle gas added is preferably the minimum amount that will sufice tocarry the necessary heat of reaction into the reaction zone and keepcarbon formation at a satisfactory low level.

The hydroforming reaction zone should be operated at temperaturesbetween about 850 and 950 F., preferably at about 900 F., and atpressures between about 50 and 500 lbs. per sq. inch. Temperatures above900 F. result in increased carbon formation and lower selectivity togasoline fractions while at temperatures below about 900 F. operatingseverity is low and would therefore require an excessively large reactorvessel. Lowering reaction pressure below 200 lbs. per sq. inch resultsin increased carbon formation which ordinarily becomes excessive atpressures below about lbs. per sq. inch. Molybdenum oxide on Zincaluminate spinel catalysts appear to be somewhat of an exception in thisregard since they give excellent results at pressures of about 50 lbs.per sq. inch. Above 200 lbs. per sq. inch, catalyst selectivity to lightproducts (Crs and lighter) increases rapidly. rl'he regeneration zone ina lluidized solids reactor system is operated at essentially the samepressure as the reaction zone and at temperatures of about ll00l200 F.The time of residence of the catalyst in a iluidized solids system is ofthe order of about 3 to 4 hours in the reaction zone and of the order offrom about 5 to l5 minutes in the regeneration zone.

The weight ratio of catalyst to oil introduced into the reactor in auidized solids system should be about 0.5 to 1.5. It is preferred tooperate such systems at catalyst to oil ratios of about 1 since ratiosabove about l to 1.5 result in excessive carbon formation. Somewhathigher weight ratios can be used at higher pressures.

Space velocity or the weight in pounds of naphtha feed charged per hourper pound of catalyst in the reactor depends upon the age or activitylevel of the catalyst, the character of the feed stock and the desiredoctane number of the product. Space velocity for a molybdenum oxide onalumina gel catalyst prepared as described above may vary from about 0.8wt./hr./wt. to about 3.0 wt./hr./wt.

The following example is illustrative of the results obtainable inaccordance with the present invention.

EXAMPLE Four samples of catalyst of essentially the same compositionwere tested in a fixed bed hydroforming unit to compare their activity.

Catalyst A was a butanol dried alumina base hydroforming catalystcarrying l wt. percent M003. A nitrogen adsorption isotherm of thiscatalyst showed only a very small proportion of the pores, if any, to beless than 50-60 Angstrom units in diameter with the bull: of the poresbeing greater than 80 Angstrom units.

Catalyst B was prepared of the same materials in the same proportions ascatalyst A except for the fact that the alumina was oven-dried at 250 F.instead of butanol dried.

Catalyst C has the same composition as catalysts A and B and wasprepared by the impregnation of a pure, commercial activated aluminathat was obtained as a product of the Bayer process.

Catalyst D has the same composition as catalysts A, B and C. It was acommercial gel type catalyst that was obtained by the rtze-precipitationof alumina and mo1ybde num oxide starting with a solution of an aluminumsalt and a molybdenum compound such as ammonium molybdate.

The several samples of catalyst were heated for 6 hours at 1200" F. andthe physical properties of the catalysts were then determined. Theresults of these tests are tabulated below in Table I.

The several samples of catalyst were used to hydroform a 200-330 F.virgin naphtha of 48.5 Research octane number in a iixed bed testingunit. The reaction zone was maintained at 900 F. and 200 lbs. per sq.inch with 1500 cu. ft. of hydrogen introduced per barrel of naphtha feedand was operated on a 4 hour cycle, i. e., naphtha feed and hydrogen gaswere passed over the catalyst at hydroforming conditions for 4 hours,after which the coke deposit was burned from the catalyst with air, andthe hydroforming process was resumed for another 4 hour period, and soon. The results obtained are summarized in Table II below, thecomparison being made at 95 Research O. N. and 10# Reid Vapor PressureGasoline.

*Weight of naphtha ieed per hour per weight of catalyst.

It appears from these data that the volume yield of C4430 F. gasoline atthe 95 0. N. level is a standoi with the several catalysts tested. Itshould be noted, however, that the catalyst A or butanol dried aluminabase catalyst possessed much higher activity permitting feed rates ofabout to 300% of those of the other catalysts tested. A furtheradvantage of catalyst A is the low carbon make. Since carbon appears tobe preferentially laid down in the minute pores of the catalyst, the lowcarbon make may be attributed to the substantial absence of small poresor pores smaller than about 50 An-gstrom units.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood, however, that the presentinvention is not limited thereto since numerous variations are possibleWithout departing from the scope of this invention.

What is claimed is:

l. The method of hydroforming hydrocarbons which comprises subjectingthe hydrocarbons at temperatures of S50-950 F., at pressures of from 50to 500 lbs. per sq. inch and in the presence of hydrogen-rich gas to theaction of a hydroforming catalyst consisting essentially of a group Vlmetal oxide supported upon a member of the group consisting of zincaluminate and alumina gel that has been dried in the presence of apartially watermiscible alcohol to give a product with a high percentageof pores having diameters above 50 Angstrom units.

2. The method of hydroforming hydrocarbons which comprises subjectingthe hydrocarbons at temperatures of S50-950 F., at pressures of from 50to 500 lbs. per sq. inch and in the presence of hydrogen-rich gas to theaction of a hydroforming catalyst consisting essentially of a group VImetal oxide supported upon alumina gel having a high percentage of poresabove 50 Angstrom units obtained by dispersing an alumina hydrosol inbutanol, converting the sol to gel and drying the resultant alumina gelparticles in contact with butanol.

3. The method of hydroforming hydrocarbons which comprises subjectingthe hydrocarbons at temperatures of S50-950 F., at pressures of from 50to 500 lbs. per sq. inch and in the presence of hydrogen-rich gas to theaction of a hydroforming catalyst consisting essentially of a group VImetal oxide supported upon alumina gel having a high percentage of poresabove 50 Angstrom units obtained by drying alumina hydrogel in contactwith butanol.

4. The process as delined in claim l in which the group VI metal oxideis molybdenum oxide.

5. The process as defined in claim 2 in which the group VI metal oxideis molybdenum oxide.

6. The process as deiined in claim 3 in which the group VI metal oxideis molybdenum oxide.

References Cited in the le of this patent UNITED STATES PATENTS2,331,353 Stoewener et al. Oct. l2, 1943 2,454,941 Pierce et al Nov. 30,1948 2,455,445 See et al Dec. 7, 1948 2,477,695 Kimberlin Aug. 2, 19492,490,287 Welty, Jr. Dec. 6, 1949 2,636,865 Kimberlin Apr. 28, 1953

1. THE METHOD OF HYDROFORMING HYDROCARBONS WHICH COMPRISES SUBJECTINGTHE HYDROCARBONS AT TEMPERATURES OF 850-950* F., AT PRESSURES OF FROM 50TO 500 LBS. PER SQ. INCH AND IN THE PRESENCE OF HYDROGEN-RICH GAS TO THEACTION OF A HYDROFORMING CATALYST CONSISTING ESSENTIALLY OF A GROUP VIMETAL OXIDE SUPPORTED UPON A MEMBER OF THE GROUP CONSISTING OF ZINCALUMINATE AND ALUMINA GEL THAT HAS BEEN DRIED IN THE PRESENCE OF APARTIALLY WATERMISCIBLE ALCOHOL TO GIVE A PRODUCT WITH A HIGH PERCENTAGEOF PORES HAVING DIAMETERS ABOVE 50 ANGSTROM UNITS.